The invention relates to a method for testing a testing device for determining a voltage condition of an on-board high-voltage electrical system of a motor vehicle.
Vehicles with electric or hybrid drive have powerful voltage sources for supplying electric drive units with energy. To reduce the thermal voltage of such a on-board high-voltage electrical system, operating voltages of 400 V or more are typically used, which pose a significant risk to operating or maintenance personnel upon contact. The voltage-free state of the on-board high voltage electrical system must therefore be ensured during repair or maintenance work on such motor vehicles.
Normally, a testing device is provided for detecting the voltage state of the on-board high-voltage electrical system. Such testing device may be integrated in the motor vehicle or may be part of an external testing device to be connected to the motor vehicle during maintenance work.
When a determination is made with such testing device that the on-board high-voltage electrical system is not live, it must also be ensured that this result is not due to a malfunction of the testing device. Therefore, the voltage state is usually observed when the on-board high voltage electrical system is switched off. When the on-board voltage decreases in this case from the operating voltage to zero, it is ensured that the testing device is working properly and the on-board high-voltage electrical system is now in fact voltage-free.
However, this can only be done when the on-board high-voltage electrical system is in a ready state. However, this is not always the case during maintenance or repair work. In these situations, there is therefore an additional risk for the service personnel.
For example, the on-board high-voltage electrical system may de-energized due to a defective contactor. When work is now performed on the on-board electrical system while relying on the voltage-free state without reliably and permanently de-energizing the on-board high-voltage electrical system by opening a service switch, then it may happen that the defective contactor closes again, so that the -board high-voltage electrical system is re-energized. Therefore, it must also be additionally ensured that the voltage-free state of the on-board high-voltage electrical system is permanent and is due to opening a service switch or another intentional interruption of the circuit.